Quantum Chemical Studies on the Spectroscopic, Electronic Structural and Nonlinear Properties of an Organic N-Methyl-N- (2,4,6-Trinitrophenyl) Nitramide Energetic Molecule

Earlier studies on the energetic molecule MTNPN show a small HOMO-LUMO energy gap. In general, the material which acquires small energy gap exhibits NLO response and identical counterparts in both IR and Raman spectra. Hence, the combined experimental and theoretical studies were performed to explore the fundamental properties of the molecule. The objective of this study was to explore the fundamental structural properties of an energetic molecule MTNPN in addition to its application as a nonlinear optical material. FT-IR technique and quantum chemical methods were used to analyze the vibrational normal modes and structural properties of the molecule. Kurtz and Perry technique is used to find second harmonic generation efficiency in comparison to the standard NLO reference material. The potential energy distribution was used to assign the vibrational normal modes of the molecule. The second order perturbation energies between the lone pair and anti-bonding species were predicted to understand the driving forces of molecular stability. The chemical reactivity of the molecule was determined from the molecular electrostatic potential surface and global reactivity descriptor results. The second-order hyperpolarizability of MTNPN and SHG efficiency of MTNPN were studied to find its NLO response and it was found from the results that MTNPN exhibits high NLO response than the standard NLO reference material. The vibrational degrees of freedom of MTNPN molecule were assigned and the experimental FT-IR spectra were compared with the scaled harmonic frequencies. The predicted second-order hyperpolarizability of MTNPN was about 6.46 times greater than the standard NLO reference urea. The interacting species between the lone pair orbitals and antibonding orbitals such as n3O8→ π*(N7-O9), n3O11→ π*(N10-O12) and n3O14→ π*(N13-O15) stabilized the molecule to a greater extent.